1. Field of the Invention
The present invention relates to digital video recorders. More particularly, the present invention relates to a digital video recorder for encrypting/decrypting video programs in segments to facilitate trick play features.
2. Description of the Prior Art
Digital video recorders (DVRs) typically store video programs on a random access storage (RAS) device, such as on a conventional hard disk drive (HDD), which enables certain “trick play” features, such as skipping ahead in a program. The trick play features are enabled by processing frame headers which are recorded in arbitrary length frames of the video program. Due to the arbitrary frame lengths, the video programs are typically processed in unencrypted form in order to detect frame headers which identify frame boundaries. Thus, prior art DVRs typically store copyrighted video programs in unencrypted form so that the DVR can randomly access individual frames during playback. This design, however, subjects the copyrighted material to unauthorized reproduction, for example, by eavesdropping while the copyrighted content is transferred from the DVR host circuitry to the RAS device.
Prior art DVRs typically employ a conventional hard disk drive (HDD), such as an IDE hard disk drive, as the RAS device since HDDs have sufficient capacity to store video content and are relatively inexpensive due to their prevalent use in personal computers (PCs). Rather than design and manufacture a customized HDD for the DVR market, DVRs are constructed similar to a PC, including DVR host circuitry for interfacing with a commodity HDD which reduces the cost of the DVR. Using a conventional HDD, however, has rendered the DVR more susceptible to unauthorized copying of video programs since the HDD can be removed and installed in another DVR or in a PC.
There is, therefore, a need to protect against unauthorized reproduction of copyrighted video programs in a DVR employing a cost effective, commodity HDD, while supporting trick play features.